Wide ranges of medical treatments have been developed using endoluminal prostheses, which are medical devices adapted for temporary or permanent implantation within a body lumen, such as naturally occurring or artificially made lumens. Examples of body lumens in which endoluminal prostheses may be implanted include arteries such as those located within coronary, mesentery, peripheral, or cerebral vasculature; veins; gastrointestinal tract; biliary tract; urethra; trachea; hepatic shunts; and fallopian tubes. Various types of endoluminal prostheses have also been developed with particular structure to modify the mechanics of the targeted luminal wall.
A number of vascular devices have been developed for replacing, supplementing, or excluding portions of blood vessels. These vascular devices include endoluminal vascular prostheses and stent grafts. Aneurysm exclusion devices, such as abdominal aortic aneurysm (AAA) devices, are used to exclude vascular aneurysms and provide a prosthetic lumen for the flow of blood. Vascular aneurysms are the result of abnormal dilation of a blood vessel, usually from disease or a genetic predisposition, which can weaken the arterial wall and allow it to expand. Aneurysms can occur in any blood vessel, but most occur in the aorta and peripheral arteries, with the majority of aneurysms occurring in the abdominal aorta. An abdominal aneurysm typically begins below the renal arteries and extends into one or both of the iliac arteries.
Aneurysms, especially abdominal aortic aneurysms, are commonly treated in open surgery procedures in which the diseased vessel segment is bypassed and repaired with an artificial vascular graft. While open surgery is an effective surgical technique in light of the risk of a fatal abdominal aortic aneurysm rupture, the open surgical technique suffers from a number of disadvantages. The surgical procedure is complex, requires a long hospital stay, requires a long recovery time, and has a high mortality rate. Less invasive devices and techniques have been developed to avoid these disadvantages. Tubular endoluminal prostheses that provide a lumen or lumens for blood flow while excluding blood flow to the aneurysm site are introduced into the blood vessel using a catheter in a less or minimally invasive technique. The tubular endoluminal prosthesis is introduced in a small diameter crimped condition and expanded at the aneurysm. Although often referred to as stent grafts, these tubular endoluminal prostheses differ from covered stents in that they are not used to mechanically prop open natural blood vessels. Rather, they are used to secure an artificial lumen in a sealing engagement with the vessel wall without further opening the abnormally dilated natural blood vessel.
Stent grafts for use in abdominal aortic aneurysms typically include a support structure supporting woven or interlocked graft material. Examples of woven graft materials are woven polymer materials, e.g., Dacron, or polytetrafluoroethylene (PTFE). Interlocked graft materials include knit, stretch, and velour materials. The graft material is secured to the inner or outer diameter of the support structure, which supports the graft material and/or holds it in place against a luminal wall. The stent graft is secured to a vessel wall above and below the aneurysm. A proximal spring stent of the stent graft can be located above the aneurysm to provide a radial force which engages the lumen wall and seals the stent graft at the lumen wall. The proximal spring stent can include hooks to puncture the vessel wall and further secure the stent graft in place.
One problem in present stent graft designs is the need to fix and/or seal the proximal end of the stent graft to the vessel wall. Fixing the stent graft to the vessel wall prevents inadvertent movement of the stent graft relative to the vessel wall. Sealing the stent graft to the vessel wall prevents fluid from bypassing the stent graft lumen and flowing between the graft material and the vessel wall. One proposed solution to this problem has been to use fasteners, such as staples or helical fasteners to attach the graft material to the vessel wall.
Unfortunately, it is difficult to accurately locate the fastener at the fixation point. X-rays can be used to view the relative location of the fastener to be installed and the fixation point, but the resolution is typically inadequate for accurate fastener placement. The fastener is small, on the order of 2-3 millimeters, and the projected image is planar, confusing the depth of the image. Contrast medium may further reduce image resolution through clouding.
It would be desirable to have a stent graft fixation system and method that would overcome the above disadvantages.